Conversion of hydrocarbons



March 21, 1933. E. F.`NELsoN CONVERSION OF HYDROCARBONS Filed June 28,1929 gllflw i ,25W/@mw dma/Ve 190372/ f/ness" Patented Mar. 21, 1933UNITED STATES PATENT OFFICE EDWIN F. NELSON, OF CHICAGO, ILLINOIS,ASSIGNOR TO 'UNIVERSAL OIL PRODUCTS COMPANY, OF CHICAGO, ILLINOIS, ACORPORATION 0F SOUTH DAKOTA CONVERSION OF HYDRO CARBONS Application led`Tune 28,

This invention relates to an improvement in processes for the conversionof hydrocarbons into more valuable products.

More particularly, the invention relates to an improvement in thehandling of cracked distillatcs produced by the thermo decomposif tionof hydrocarbon oil whereby more suitable products are obtainable fromthe cracking process.

In the operation of commercial cracking processes, the resulting liquiddistillate withdrawn from the receiver is charged with dissolveduncondensible gas and light hydrocarbons which are highly volatile. Inoperation, suiiiciently converted vapors which do not condense below acertain point are removed from the usual dephlegmating or fractionatingzones of the cracking process, and these vapors together with theuncondensible gas formed in the process are condensed. This distillateand uncondensible gas collects in a receiver, the gas being removed fromthe top thereof and the liquid distillate from the bottom. It is thisdistillate which is found to be charged with dissolved uncondensible gasand highly volatile light hydrocarbons.

According to one of the methods used at present, the non-condensiblega's removed from the receiver is passed through a gas separator. Thus,it is obvious that the use of a receiver with a gas separator permitsthe gas escaping from the receiver to carrywith it considerablecondensible fractions. In the chemical treatment, pumping operations'and storage of distillates of this character, the dissolvednon-condensible gas and very light distillate are lost by evaporation.With the escape of these constituents by evaporation a certain portionof the desirable relatively heavier constituents of the distillate arecarried away as well, so that the resultant loss is not only of theundesirable wild constituents, but also of certain desirable light endsof gasoline which by the employment of my invention may be saved.

It is a primary object, therefore, of the present invention to stabilizeboth the noncondensible gas and condensed distillate so that thenon-condensible gas may be stripped of substantially all of thecondensible frac- 1929. Serial No. 374,471.

tions and thus be substantially dry, while the distillate will bestripped of substantially all of the non-condensible gas and Very lightends.

As a feature of the present invention, the stabilization of the gas andthe distillate may take place under plant pressure, that is, thepressure within the stabilizer may be the same as the pressure on thecracking process which produced the distillate and non-condensible gas,or it may be reduced relative thereto.

In one specific embodiment of my invention, I employ a tower or othersuitable means as a stabilizer element to stabilize the noncondensiblefractions from the pressure distillate. The latter may be thenchemically:

treated, transferred and stored with mininum loss of the desirablecomponents thereo Other advantages and objects of the invention will bemore apparent from the following description.

By reference to the single figure in the drawing, which is adiagrammatic side elevational view of apparatus in which the process maybe carried out, the operation will be obvious to those skilled in theart.

Referring more in detail to the'drawing, raw oil may be supplied throughline 1 by means of pump 2 and adephlegmator 3, where it is preheated bypartially condensing the vapors entering the bottom thereof, as will behereinafter described. A hot oil pump 4 taking suction from the bottomof dephlegmator 3 through line 5 delivers the preheated oil and refluxcondensate to a heating coil 6 located in furnace 7 and heated by meansof burner 8. This furnace may be of any design suitable for heating theoil in coil 6 to the desired temperature. The heated oil passes outthrough transfer line 10, in which is interposed valve 11, to eX-pansion chamber 12. Vapors separating from non-vaporous products inchamber 12 may pass out through vapor outlet line 14,

controlled by valve 13, discharging in the line 15, controlledby valve16,y into condenser coil 17. Unvaporized residue may be withdrawn fromthe chamber 12 through line 9, controlled by valve 9.

The distillate and uncondensible gas pass out through Iline 18 throughstabilizer 19, which may be of any suitable construction, wherebyintimate contact of vapor liquid may be obtained in order to arrive atequilibrium conditions. lf stabilizer 19 requires heating, means such asa steam coil in the bottom thereof, as indicated at 20, may be rovided.

ne of the novel features of the present invention takes advantage of thefact that the uncondensible gas escaping through line 21 will, throughreduction in pressure by means of valve 22, become greatly cooled,depending upon the differential pressure employed between the stabilizer19 and the pressure prevailing in coil23. If necessary, all additionalcooling element may be einployed, such as a coil 24 located at or nearthe top of stabilizer 19. If Vall of the expanded 'gas is not necessaryto obtain the requisite cooling, then regulated portions thereof may bepassed through coil 23 and the remainder diverted from the coil by meansof by-pass line 35, controlled by valve A direct gradient willnecessarily prevail between the point at which line 18 enters thestabilizer and the top of the tower. Likewise, a direct gradient willprevail from the leating means at the bottom of the tower to the pointat which line 18 enters the stabilizer; or, in other words, a gradientwill prevail more or less uniformly from the bottom of the stabilizer tothe top.

The uncondensible gas passing through coil 23 will, at reduced pressure,pass out through line 25. The stabilized condensate from the bottom ofstabilizer 19 may pass out through line 26 and cooler 27 into receivingdrum 28 from which the condensate may be withdrawn through valve 29. Bycontrolling the temperature conditions at the top of dephlegmator 3 a.portion of the condensate may be withdrawn from receiver 28 and forcedthrough line 30 and valve 31 by pump 32. Provision is made through valve33 for releasing gas from receiver 2S. which gas, under normalconditions, will not be liberated at the top of stabilizer 19 throughline 21, pressure on the system being controlled by valve 22; that is,valves 11, 13 and 16 will be open. y n

In an alternate method of operation, by the employment. of the valvesjust mentioned, differential pressures may be einable one. sincematerial pressure reduction through valve 22'in line 21 is desired toget and a proper cooling elect for the top of stabilizer 19. Since gasrelief valve 33 on receiving drum 28 will not normally be in use, theliquid level in stabilizer 19 should be ascertained by means of a gaugeglass 34 located on the bottom thereof.

It will be understood that, by means of the present invention, apractically complete stabilized distillate may be recovered from thebottom of stabilizer 19; with the fixed gas discharging from the top ofthe stabilizer containing practically no gasoline-like material. By thecontrol of pressure reduction by means of valve 22, and by means of thecooling means 21 and heating means 20, the character of both thestabilized condensate and the uncondensible gas leaving stabilizer 19may be varied within relatively wide limits.

As an example of the conditions prevailing in one operation employed inmy invention, a 24 B. gravity Mid-continent reduced crude oilfinay becharged to the cracking unit. The temperature of the discharge ofheating coil 6 may be approximately 910 F.; the temperature at the topof dephlegmator 3 may be approximately 525 F.; the temperature of thecondensate and non-condensible gas entering stabilizer 19 through line18 ma be approximately 95 F.; the temperature o the gas exiting from thetop of stabilizer 19 may be about 75 F. Steam may be employed at thebottom of stabilizer 19 1n coil 20 so that the temperature of thestabilized condensate leaving through line 26 may be about 165 F. aiidby passage through, cooler 27 may be reduced to approximately 85 F.

Pressures prevailing in the system may be approximately 275 pounds tothe square inch at the discharge of pump 4, while the stabilizer may bemaintained under a ressure of approximately 190 pounds, the di erencebetween these two pressures being due to hydroy static head and frictiondrop. The pressure may be reduced by valve 22 to substantiallyatmospheric, or )ust enough above atmospheric to overcome friction inpassing through the, remainder of the apparatus. This pressure reductionwill bring about a corresponding temperature reduction of F., whichunder these specific conditions, will be sufficient to condensesubstantially all of the portions ascending in tower 19 when broughtinto contact with the cooling coil.

A yield of about %4 pressure distillate will be obtained having aninitial boiling point of approximately 110 F. and an end point of about,550 F., containing about 73% of 437 F. end point gasoline. Theiiiicondensible gas in stabilizer 19 discharged from line 25 willcontain, by the charcoal test, less than a gallon of coiideiisiblegasoline per thousand cubic feet. In operation without the stabilizer`under the saine conditions, the fixed gas from the. receiving'drum 28will show a gasoline content of approximately two gallons per thousandcubic feet. A material loss will also occur by reason ofthe fact thatthe distillate will have an initial boiling point of about 90 F. andwill show a vapor loss in handling and treating of approximately 2%.

It is to be understood that the specic figures given in thisillustrative run are not to be taken in any sense as a limitation of theinvention. The figures are merely illustrative of one specificembodiment of the invention.

The invention in its broad concept contemlates, first the separation ofthe uncondensil le gas from the liquid distillate under superatmosphericpressure, the subsequent reduction in pressure on said uncondensible gasthus bringing about a corresponding decrease in temperature, whichdecrea in temperature is utilized as a cooling medium to stripcondensible fractions from the gas during' rthe separating step.

I claim as my invention:

1. In a process of hydrocarbon'oil conversion wherein said oil is heatedto cracking temperature and 4suiiciently converted va-- pors andnon-condensible gas separated from insuiiciently converted vapors andresidue, superatmospheric pressure is maintained on said oil and vapors,and said suiliciently converted vapors and non-condensible lgas arecondensed and cooled', the improvement whichl comprises separating theuncondensible gas from the condensed distillate under superatmosphericpressure in a separating zone, removing said separated gas from theseparating zone, reducing the pressure thereon to thereby reduce itstemperature, and returning regulatedportions of said gas under reducedpressure to said se arating zone and passing same therethroug rectcontact with the gas being separated therein to condense condensible"portions associated with said gas. c

2. Inv hydrocarbon oil pressure cracking processes vwherein the crackedvapors and gases are cooled under superatmospheric pressure to condensethe vapors, the improvement which comprises ingoducing the condenseddistillate and gas to a stabilizing zone maintained under thesuperatmospheric pressure of the cracking process, separating the gasfrom the distillate in said zone, Vremoving the separated gas underpressure from the sta-` bilizing zone and reducing the pressure thereon,and passing the expanded gas in indirect heat exchange relation with thegas being separated in said zone.

In testimony whereof I aix my signature. j

EDWIN F. NELSON.

